Jove
Visualize
Contact Us
JoVE
x logofacebook logolinkedin logoyoutube logo
ABOUT JoVE
OverviewLeadershipBlogJoVE Help Center
AUTHORS
Publishing ProcessEditorial BoardScope & PoliciesPeer ReviewFAQSubmit
LIBRARIANS
TestimonialsSubscriptionsAccessResourcesLibrary Advisory BoardFAQ
RESEARCH
JoVE JournalMethods CollectionsJoVE Encyclopedia of ExperimentsArchive
EDUCATION
JoVE CoreJoVE BusinessJoVE Science EducationJoVE Lab ManualFaculty Resource CenterFaculty Site
Terms & Conditions of Use
Privacy Policy
Policies

Related Experiment Videos

Recrossings and transition-state theory.

Huw O Pritchard1

  • 1Department of Chemistry, York University, Toronto, Canada M3J 1P3.

The Journal of Physical Chemistry. A
|July 13, 2006
PubMed
Summary

Classical trajectory calculations reveal frequent recrossings over reaction barriers for NCCN and CH3CN isomerization. This suggests transition-state theory may overestimate reaction rates, with a transmission coefficient kappa = 0.5 for NCCN isomerization.

Related Concept Videos

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by
Same author

Eigenvalue methods for unimolecular rate calculations with several products.

The journal of physical chemistry. A·2007
Same author

On the atmospheric oxidation of liquid toluene.

Physical chemistry chemical physics : PCCP·2006
See all related articles

Area of Science:

  • Chemical Kinetics
  • Computational Chemistry
  • Reaction Dynamics

Background:

  • Classical trajectory calculations are essential for understanding chemical reaction dynamics.
  • Isomerization reactions like NCCN <==> NCNC and CH3CN <==> CH3NC are fundamental in chemical processes.
  • Recrossing events can significantly impact the accuracy of theoretical reaction rate predictions.

Purpose of the Study:

  • To investigate the frequency of recrossing events in NCCN and CH3CN isomerization reactions using classical trajectory simulations.
  • To compare long-term mean residence times with mean first passage times to evaluate reaction dynamics.
  • To determine the implications of recrossing events for the transition-state theory transmission coefficient.

Main Methods:

  • Performed long-duration classical trajectory calculations (up to 0.2 microseconds) for NCCN and CH3CN isomerization.
  • Defined and quantified 'recrossing' events as barrier passages followed by return to the initial well within 0.2 picoseconds.
  • Calculated and compared mean residence times with mean first passage times for reactant and product wells.

Main Results:

  • Observed significantly more recrossing events than actual reactive events for both NCCN (2:1 ratio) and CH3CN (10:1 ratio).
  • Found that for NCCN isomerization, mean residence times were approximately twice the mean first passage times, except at low energies.
  • The observed ratio of residence times to first passage times suggests a transition-state theory transmission coefficient (kappa) of 0.5.

Conclusions:

  • Recrossing events are prevalent in these isomerization reactions and can lead to overestimation of reaction rates by standard transition-state theory.
  • The results indicate that the transmission coefficient for NCCN isomerization, under the conditions studied, is approximately 0.5.
  • Accurate modeling of chemical reactions requires careful consideration of trajectory recrossings and their impact on calculated rate constants.

Related Experiment Videos